Opto-electronic elements alter their electrical condition responsive to the application of light and vice-versa. Such elements include light emitting diodes which emit light when electrically energized. A light emitting diode may be used to actuate a phototransistor or light actuated controlled rectifier which alters their current conducting properties upon the application or removal of light. Because of the optical coupling between such opto-electronic components, good isolation between input and output circuitry or power and control circuitry may be obtained, as well as other advantages such as enhancement of the miniaturization obtainable with thick film conductor circuitry mounted on a ceramic substrate.
The required optical coupling depends on juxtapositioning the opto-electronic elements so that the light emitted from one falls on the photo sensitive portion of the other. In the past, one technique for obtaining the necessary alignment has been to bend a lead frame element to provide proper positioning for the transmission of light between light emitting and light responding elements mounted on the substrate. Reference is made to Kaufman's copending application, Ser. No. 825,619, filed Aug. 18, 1977, now U.S. Pat. No. 4,156,148. In some constructions, one element is placed in a cavity bridged by the other element, as in U.S. Pat. No. 4,011,859.
However, it is now apparent that such techniques, while quite satisfactory, can be improved upon. The prior art did have some inflexibilities in design. For example, those applications using bent lead frame elements were limited to those locations where such lead frame elements were located. This was typically along the edge of the circuit substrate. Use in the interior of the substrate required special routing and design of the conductors to maintain circuit isolation between the uninsulated components. Further, the components were often hard to adjust to obtain the accurate alignment necessary for optimum optical coupling.
It is, therefore, the object of the present invention to provide an improved mounting arrangement for light responsive and light emitting elements to obtain their optical coupling. The arrangement of the present invention is highly flexible in location and use and permits accurage alignment of the elements.
In the present invention, a light responsive device, such as a light actuated controlled rectifier, is connected in one thick film conductor circuit and a light emitting element, such as a light emitting diode, is connected in a second separate thick film circuit. In one construction, the controlled rectifier is mounted on a non-conductive substrate while the light emitting diode is mounted above the substrate and optically coupled to a photo sensitive area of the controlled rectifier by a pair of arms which cantilever from spacers connected to the thick film conductors of the second circuit. The arms may be formed from lead frame elements and the spacers may be separately or integrally formed with the arms.